In the UK, electrical appliances connect to the mains electricity with a three-pin plug. Each pin has a wire with a unique colour, which makes it easy to identify.
The features of a plug are shown below.
Each wire is made from copper, so it can conduct electricity. For safety, they are coated in a layer of insulating plastic. Let’s look at an actual plug:
The table below highlights the properties of each of the 3 wires.
|Live||Carries the alternating potential difference from the power supply.||Brown|
|Neutral||Takes the electric current back to the source to complete the circuit.||Blue|
|Earth||This is the safety wire.|
There can be an electrical fault in the circuit, which could happen when the live wire loosens and touches the casing.
To prevent this, the Earth wire gives the current an alternative path to flow, which also prevents the appliance from operating.
|Green and yellow|
As you can see in the table below, the potential difference between the live wire and both the neutral wire and the earth wire is 230 V.
|Wires||Potential difference between them (V)|
|Live and neutral||230|
|Live and earth||230|
|Neutral and earth||0|
The current is able to flow into the neutral wire and earth wire because the potential difference between them is 230 volts. The human body is typically at 0 V, which makes the live wire very dangerous, as there is a large potential difference between the live wire and the human body. So, the large current can flow through us to the earth, giving us a large electric shock.